Techniques Involved in Studying Receptor Dynamics

Receptor population is dynamic and is exemplified by their rapidly changing expression in neuronal cells, receptor internalization with steroid ligands and growth hormones, and their upregulation and downregulation as in β2 receptors. Fluorophore tagging to recombinant receptors and their visualization in cultured cells represent a way by which movement of receptors can be traced. However, the linking molecules between receptor and fluorophore are bulky. “Single molecule” tagging has been made possible by creating mutated receptors using unnatural amino acids that preserve function as well as they act as handles where luciferase enzyme can bind. Apart from tracing fluorescent activity, the surface receptor density in neurons can be estimated as being proportional to the electrical activity measured (“functional” tagging). These methods have been crucial in understanding how receptors are cycled in their lifetime.